In radio networks, for example in mobile radio networks, transmission errors typically depend on the quality of reception. Several concepts have already been known in the field of conventional technology which improve the error-proneness of data transmissions, for example by taking advantage of diversity. For example, current radio transmission systems such as UMTS (universal mobile telecommunication systems), HSPA (high speed packet access), LTE (long term evolution), etc. are trying to make use of the available transmission bandwidth as well as possible by adapting a user's data transmission rate to the channel quality. For this purpose, loops may be used, i.e. a user measures the channel and reports the channel state, so-called CSI (channel state information), to the network, i.e. to a base station or node B.
Modern transmission techniques such as utilizing several transmit or receive antennas, so-called MIMO (multiple input multiple output), space-time multiplexing, so-called space-time codes (STC) or spreading techniques, for example, are used for increasing transmission rates, or for increasing coverage or rendering it more reliable.
In the field of multimedia applications, transmission of audio and video data is becoming increasingly important; for example, coding methods are constantly being developed further. In the field of video coding, concepts of scalable video coding, cf. AVC (advanced video coding) and SVC (scalable video codec) have been known, which also endeavor to make use of an available data rate as well as possible.
Video transmission in mobile radio networks constitutes a problem. Since video broadcasting, such as television programs, is constituted by broadcasting data, no individual feedbacks on the part of subscribers are available. In other words, a broadcast transmission is directed at a multitude of users, which does not allow obtaining individual feedback on a transmission quality from each user. Conventional concepts enabling broadband wireless video transmission in cellular mobile radio architectures at low transmit power both with a large range of transmission and with a high level of failure safety cannot be used in the case of broadcasting due to lack of feedback from the individual subscribers.
Frequency-selective multipath channels place high requirements on the transmission methods. New techniques such as MIMO, frequency-selective scheduling as well as space-time coding, for example, may often use feedback on the channel quality at the receiver in order to be able to be used in an optimum manner.
Conventional broadcasting concepts use DVB (digital video broadcast), for example; specifically, e.g. for DVB-T (T=terrestrial) television. For example, in this concept several exposed locations are used as base stations, and a video signal coded by means of MPEG-2 (Moving Pictures Expert Group 2) is emitted by means of a multi-carrier process such as OFDM (orthogonal frequency division multiplexing). However, the broadband radio channel is subject to the propagation conditions that are typical for mobile radiocommunication. Due to the multipath propagation, parts of the signal may erase themselves by destructive superposition and may induce so-called fast fading. The resulting transmission or bit errors at the receiver may be corrected by adding redundancy, i.e. within the context of channel coding—however, this will be at the price of slower transmission rates.
Shadowings of direct line-of-sight links, which may also be referred to as slow fading, may lead to considerable drops in the receiving power, even in small regions, in the order of magnitudes of several meters. To counteract this, high transmit powers are sometimes used for DVB-T, for example more than 100 kW at a bandwidth of 5 MHz. Nevertheless, the term “mobile television” is justified only in the vicinity of the base station, i.e. up to a distance of several kilometers from same. If larger distances are to be covered, antennas specifically directed to the transmitter may be used in most cases.